A Mamba's Venomous Breath
by DownwardDive
Summary: The final stand between a seemingly eternal war between Good versus Evil ensues; the light beginning to slowly die out until one man takes actions into his own hands. A snake always sheds its skin, and for him, this will be the mark of a concluding battle—one where evil shall no longer prevail. Based off of the latest events in Chapter 188. One-Shot!


This will be my own alternative one-shot take on the succeeding chapters to the latest Manga events, from Chapter 188, and what I believe would be a good scenario. If you aren't currently following the manga, I'd suggest you avoid this as this contains spoilers. However if you do, please review and criticize if needed as I would appreciate this.

Also shout-out to SkywardStrike, the author of Branching Paths, an alternative universe where Nezuko and Tanjirou were separated upon the former's demonification—leading to a dark but unique twist to the series from the matter's perspective. I assist him with some ideas, but he's been generous enough to give me shout-outs as well, so I'd be glad if you all gave him some support.

So sit back and enjoy.

* * *

Everyone never knows who they really until they are the nearest to death; the proud become humble, the kind become selfish, the weak become strong, and the narcissistic realize that they are indeed mortal. It either breaks the individual completely or piece together the remaining fragments that they would continuously be searching for if they hadn't reached the point of the end.

In this case, the fear of death was imminent all around; the blood of his comrades shed and the carcasses of his subordinates scattered like gruesome decorations across the battlefield. As insensitive as it may seem to be used to it from the perspective of experience, it also proved that one can handle quite a bit of stress once they have adapted to it. However, everyone has a breaking point and an animal who is backed into a corner will not hesitate to go all out.

Seeing the woman of his dreams—the woman who had given him hope despite his bad experience with the gender that practically ruined his life before this point—be severely wounded and with him being unable to protect her… this brought forth an anger beyond anything he could fathom previously.

Hopelessness turned into rage as he set his sight onto the man—no, the _demon_—who was the cause of every problem in this dystopian world that he only knew. Hissing in synchrony with the reptile coiled around his neck, his scarred lips pressed against one another in an indescribable seal of a frown. His breathing began to flow into an unusual pattern as he began to hiss out his next plan of action.

"_Breath of Snake: Third Form: Coiling Cobra!_" The afterimage of his physical form appearing in place as his speed more than doubled, almost tripled, as he danced around the whip like slashes of his opponent, delivering his multiple fast paced slashes of many angles at the vital spots.

However, this was no mere human as the being was able to instantly regenerate from this and kick the man directly in his chest, flying him across the landscape, scathing along the ground at uncontrollable velocity. After the long journey, he came to a halt in a recovered somersault as he heaved heavily - more wounds bathing his already bruised body. Yet, he said nothing, keeping any thoughts internal as he studied his opponent for a weakness.

"Obanai-San! Do not charge in alone for Muzan is to great of a foe for anyone of us to handle all alone! Regroup quickly so we can rethink our strategy…!" The thunderous cries of the beaded giant known as Himejima was instantly put on hold before the sentence could be completed.

"To hell with this! I'm tired, we all are! What good are we doing if we're just playing cat and mouse in rounds with an enemy that is practically immortal? If you're afraid to sacrifice a piece, then you'll never capture the King!" The cold and piercing voice cut sharply through the air as everyone present was curious by what he meant. They lost a lot today: Muichiro, Genya, Shinobu, Tanjirou and Tamayo as the noticeable examples. That, and the main objective was yet to be completed on such limited firearm.

His body began to shake quietly as he head was kept down, the tears building up in his eyes. Why was he even threatening to cry, was he at his mental breaking point or was he afraid of the decision that he was about to make?

"We all lived painful lives up to this point, and we have no guarantee if our future ends here today, but for the sake of others and the upcoming generation; we must rid this beautiful world of such foul evil. If it means one life taken for the safety of a thousand more, then by all means will I take this!" His gaze becoming laser focused on the bored form of his opponent who only return an empty and dull state of underlying arrogance and pure malice.

"A snake's skin sheds to mark the point of its rebirth, and if this day means that the world shall return to the light that it once had, then let me be that point!" Within an instant, he dropped to one knee as he stabbed the ground below him with his strange blade. Without pause, his snake uncoiled itself around his neck and began to wrap itself around the blade in an ascending but careful manner.

"_Now, Kaburamaru_!" The announcement was met with the sudden stretch of the snake who met its cruel fangs to his owner's neck, biting down into the delicate flesh. Wincing only the slightest that he could muster, Obanai began to intensify his gaze at the ground below as he began to sweat profusely. The poison inflicted from Muzan was already enough to deal with - but this was on an entirely different scale. His heart raced to unbelievable speeds as his blood pressure spiked within seconds of this happening. It felt like every organ of his body would not tolerate this stress as he fought hard to not drift into the constant state of unconsciousness.

However, slowly but surely, scale like marks would appear across his face—making him reptilian in nature slowly. His eyes were shut close as a result of this intense metamorphosis. His breathing began to calm slowly despite being intense as his bleeding began to stop, his wounds almost seemingly closing up. Raising his head once more, the sudden changes began to shock the other Demon Slayers as they realized that Obanai too, had indeed received the Mark of legend.

"If five minutes is all that I have until I breathe my final breath, then I'll have you regret that the sun didn't rise sooner instead! **Prepare to meet the gates of hell!**" His eyes would open to be met with a sharp pupil of a reptile that seemed like it could pierce more than his own blade. What was shocking was the pressure exuding from him that his colleagues could sense… whoever this was, he and the previous Obanai were on entirely different planes of power.

Muzan simply cocked an eyebrow before stuttering a small giggle, only to eventually throw his head back and scream a laugh to the heavens. "All you insects do are just talking big, get in the way and eventually die and do nothing! You demon hunters are disappointing, mere children who try to make a difference when you can't! So what my legion is dead if a God such as me can wipe you all out by myself?"

Then he stared at all of them with a look of pure hatred that was set in stone, "That's why when I send you all to hell, the experience there will feel like paradise compared to what you're about to receive." However, when he looked back to where the snake-like man was, he was seemingly gone. Then, for the first time ever, sheer horror fell upon the expression of the all-father of demons.

"What was that you said? Well if that's the case, I'll simply give you your throne over there, because if I'm going to die, I'll be dragging you there with me." The mere whisper sharpened throughout the ear like a cold commandment, as Iguro twirled his sword before sheathing it into the scabbard, all while having his and Muzan's back facing one another.

Then, blood began to spray everywhere as the delayed slashes occured onto his back as his arms were nearly cut off in the process. Without wasting a further minute, Iguro spun on his heel and delivered the most powerful roundhouse kick to Muzan, flying the demon rocketing forward as he grunted as a response. While flying forward, he wondered how that weakling got so strong suddenly, and before he could read his thoughts out loud, he was met with the cold gaze of the swordsman whose body was parallel to his while they both were flying in the trajectory of where the kick sent the monster.

Clenching his teeth, Muzan was about to clasp his hands to crush the arrogant boy's head, but he was met with the silent statement of, "Breath of Snake: First Form: Weaving Slash." Cutting Muzan's hands off without any hesitation, and then disappearing in the next second. Eventually, Muzan was able to land on the ground and break his fall with a somersault, as his feet skid across the ground somewhat gracefully. His wrists bled profusely for a few moments before they healed to full recovery.

It was quite apparent that Muzan was absolutely aggravated by the annoying insect that had got two good shots on him. He wasn't expecting the man who should've been slowly withering away by his injected poison to get this strong suddenly. He didn't know how, but this was the first time he saw such a drastic effect of a mark's power boost. If he could say with a fact, when he stared deep into his opponent's soul, he could guarantee that as of right now, he was now the strongest of those bugs present.

Then in the next minute, Muzan went on his knee as his left ankle was cut off—a gasp ghostly leaving his lips as the surprise was too much to hide anymore. Turning around, he looked up and saw it… the vision of the man who caused this all. His reptilian like eyes gazing deep within the soul of his that had probably been lost all those years ago. His blade emanating under the last fragmented essence of the moonlight, all while his snake bared its fangs at him.

In a quakering tone, Muzan's cells activated as he shook in fear—While he was different, they both came had him in a submissive position, each with their blade ready to strike down at him—"Who are you… you were not this strong a while ago! What did you do?!"

Cocking his head to the side, the scarred swordsman simply pointed down at the demon with his blade, his eyes empty of all emotion that was not contained hatred, "Weren't you the one who was cocky just mere moments ago? Look at you, cowering at my very feet. Remember all the lives you took, the pain you caused, and the despair you took in with much intoxication."

Fixing his head, his eyes darkened even further as he snarled at the man, his knuckles whitening as he gripped his sword with even more determination, "This is your end, Demon!"

The next minute, Muzan was kicked into the air with the now enhanced speed of the swordsman as time seemed to slow for him, barely able to process how this was happening to him of all people. The evil aura began to intensify as Muzan flipped himself back into position whilst still travelling mid-air, looking down at the swordsman who crouched on the ground in a ready stance.

With a mighty leap, Obanai held his blade positioned at his left waist as his eyes locked firmly with his opponent. With a grunt, Muzan targeted his flesh spears out with even more power to stop the tracks of the swordsman who was coming toward him. Ascending, Obanai was ready to slash at them when suddenly, he began to hack out blood violently. Grinding his teeth, he changed his attack into a defend as he pushed against the violent onslaught of Muzan.

* * *

"Obanai's in trouble… what happened? He just had the advantage a while ago!" Sanemi was concerned, it was like all hope was lost whenever it finally showed light. In response, the firm hand of the gentle giant, Gyomei, clasped onto the scarred warrior's shoulder.

"It looks like Iguro-san injected a powerful venom within him that would give him the properties of the mark, except one that would be more powerful than the likes of us would eger possess. However, he is indeed pushing the limits of the human body as the venom is causing unbearable strain on his organs, as they try to recuperate against this. Coupled with the fact that he is not in the most ideal of situations… this is a suicidal last stand that he will not be coming out alive from."

Tears streamed down Gyomei's face as he peered into the anatomy of his colleague with the ability of the See-Through World. It was clear as day for even someone as blind as Himejima, Obanai's heartbeat was far beyond what was considered dangerous for a human being—and his lungs were working overtime to bring in as much oxygen to the circulating race track that his blood was being at the moment. If he were to estimate, Obanai had less than a minute before his body would fail completely.

* * *

With his sword pressed against the overwhelming of Kibutsuji's spears, Obanai was cussing silently under his breath as he was struggling to fend them off. He knew he had little time as he could feel the pain, his consciousness threatening to slip away at any minute. Grinning at the struggles of his now weakened prey, Muzan retracted his weapons before sending them out with full force as Obanai could only stare in disbelief as they flew straight to his chest.

Was this his end… was this how he would die? All this previous bravado for nothing. He could see his life flash before his eyes. His captivity that the scum known as his family placed him in, his escape from the snake demon, Kyōjuro helping him enroll into the Demon Slayer Corps, him being promoted at the Pillar Ceremony, meeting Mitsuri for the first time, and all his times spent around her as they both worked together to slay demons together.

A tear rolled down his eyes as he saw the attack coming to finish him off. What would finish him off first; Muzan's blades or his body failing him completely? With his eyes slowly closing, his vision began to overwhelm with darkness; his last resonance of peace before the pain would overwhelm him.

However, it would never come as he was instead met with the pained gargles of a green-haired boy as the blades pierced through his torso violently; stopping mere inches from Obanai. His eyes widened, he seemed like a Demon Slayer yet he held no sword in his possession. His confusion was ended when he was met with the slit pupils and darkened sclera of the punctured youth in front of him.

"You idiot, you don't have time! Finish him or everything will be in vain!" For that moment, their eyes locked, Obanai knew that this boy seemed to have lost everything… the same emotion he held when Mitsuri was injured mere moments. However, while he may not know what happened to the boy… he know he had hope for Mitsuri as long as he finished what he began earlier.

Falling back to the ground, Obanai somersaulted in the air before using the earth below as a platform to leap on—exploding with much more force than he did the first time around. His body rocketed toward Muzan who was in shock, as to what happened. The boy who troubled Nakime; how was he still alive after he personally blew the latter up? Without much questions to be asked, he could only look in shock as Obanai inched closer to him, his blade slowly revealing itself as his opponent swerved his body slightly.

"_**Breath of Snake: Final Form: Black Mamba**_!" When his blade bared it's form for the final form, Muzan eyes widened, the blade that his opponent was flying toward his neck was completely different than before… it was now a deep red! The last thing that he saw was Obanai slashing toward him as the illusion of a humongous snake enveloped the background behind him.

All he could feel was pain as his body was slashed apart at several different angles; everything severing apart as Obanai passed straight beside him, the latter finally sheathing his blade for the final time. Blood began to spray violently from Muzan as his body was bifurcated at several angles cleanly, his head slowly falling to the ground as he was decapitated even. The last thing he uttered was—as the head began to spin and look up and glare one last time at the back of the man who caused this all—"Damn you, Obanai Iguro!"

Obanai himself hacked out blood as he was bleeding from every orifice, his body finally taking its toll. He could feel something different about him just before he attacked Muzan… he could see into the very anatomy of the demon. It was so strange, he could see the seven hearts and five brains that this weird monstrosity possessed. He had targeted his final attack to slice at all of his vital points, and he was praying that he was successful as the pain bared down at that very crucial moment.

'Mitsuri… I'm guessing this is it for me. Himejima-san, Shinazugawa-san… even you two; Tomioka-san and Tanjirō. I'll be leaving this world for you lot to reshape. I'm coming, Rengoku-san, Tokito-san, Kocho-san and Ubuyashiki-san.' His thoughts gleaned over as he cracked out a final, bloody smile.

"Our… chapter… ends… here, Kaburamaru." With a hiss as his response, Obanai closed his eyes, nodded his head, and breathed one final time as his limp body began to descend rapidly to the ground. However, unlike Muzan, his body never crashed violently as he was caught by the scared figure of Murata; falling gracefully into his arms.

"Iguro-san… I'm sorry… I'm sorry that I could not fight alongside you. You may have been harsh in your training, but your final stand against Muzan was remarkable… you saved us all!" Tears streamed uncontrollably from the young man as he cradled the dead form of the swordsman who may have saved them all. All the remaining fighters around were in shock at the final moments… Did Obanai really defeat Muzan? Was he really dead?

All that could be heard were the uncontrollable wails of Mitsuri as she laid nearly paralysed on the ground. "Obanai can't be dead! Not today, we've lost so much! I won't accept it, he has to be alive! Not today, I'm not losing him. Not today when I was unable to confess that… that I loved him all along!" The pink-haired girl would only continue to cry as everyone around simply responded by staring at the ground below.

The indeed lost a lot today… most of the Ubuyashiki family, Muichiro, Shinobu, Genya, many soldiers, Tamayo, Tanjirō, and now Obanai. However, today may have marked a new hope for the world as Muzan may seemingly be dead…

* * *

"Did you really believe that this would be enough to kill me?" Everyone turned their heads sharply to where cold voice originated from, and standing product with his white hair gracefully down onto his shoulders, was the revived form of Muzan Kibutsuji. Slowly walking toward the form of a petrified Murata, he simply grew a devilish smile.

"That red blade, the mark and that form… if I didn't know better, I'd say you reminded me a lot of that man, Yoriichi. However, you don't hold a candle to him, and yet he couldn't defeat me. However, I'll give you one last thing… beside him, you're the strongest person that I've faced to this date. Now be honoured to be eaten by me, Iguro-san." With a mocking tone of courtesy, several attached spears began to grow out of his back as he slowly closed the distance between him and Murata.

The latter slowly stepped back slowly as he began to panic as to what was happening. Didn't Obanai just kill this monster? What was happening? How many more lives would be lost? Would they lose tonight… was this really the end? He could think no more as he tripped over and fell down on the cold ground below; Obanai's body still secured as Murata broke the fall instead. Just a few meters away, Muzan's blades rose readily as they almost seemingly were happy at the aspect of the brutality that would soon follow.

Kaburamaru could only weakly hiss at the blades before collapsing onto the torso of his dead master, the strain having caught up to him, as his spirit left his small body to meet up with his master in the afterlife. Murata was shaking, he didn't know what to do… there was not anything that he could do, as he was far too weak to save them. The other pillars were all racing toward Murata but they were far too slow, far too injured, and they could do nothing as the blades reached the young swordsman.

That is until five simultaneous calls echoed throughout the battlefield with all of the blades being either parried, detached or knocked away.

"_Breath of Flower: Second Form: Plum Spirit!_"

"_Breath of Beast: Fifth Fang: Mad Cleave!_"

"_Breath of Sound: Fourth Style: Death Knells of Avīci_!"

"_Breath of Flames: Fifth Style: Flame Tiger!_"

"_Breath of Water**: **Sixth Style: Twisting Whirlpool!_"

The harmonious effects of these combined attacks was enough to completely defend the once threatened swordsman, with all of the spears laying waste on the ground. However, Murata would open to see himself sitting on the ground beside Mitsuri, with Obanai's body no longer in his possession. Instead, the latter laid completely peaceful with his hand being caressed in the mournful hand of the injured beauty.

"What happened…?" Before he could say anymore, all he could see was a green checkered jacket of a red-haired man. However, just for a brief moment, when the latter turned his head to face him; he could swear that he saw an older man with red hair, a matching coloured jacket, and a slightly different pattern to what the youth usually possessed. It was him, it was Tanjirō Kamado from the dead, but he seemed so different and stoic.

"Murata, could you please transport Mitsuri and Obanai's body off the battlefield? As much as I'd like her to fight alongside us, she's going to be more of a liability to us and I'd rather no more lives to be taken." The command was as clear as day despite it almost being a faint whisper, and for once, Murata could only feel submissive to what he heard. Indeed, this was not the same Tanjirō he knew, but a man who was ready to finish this entire war.

Turning his head, he could see a black-haired girl with orange tips, a pink kimono underneath a brown jacket, and her fangs that didn't quite seem in place for her innocent pink eyes. She was placing her hands onto Mitsuri, and for a moment, flames appeared above the matter's wounds as both she and Murata himself were in utter shock as to what was occuring. However, it was apparent that her wounds were healing as the bleeding was stopped. Whatever she was… she was not an ordinary human, but it was clear that she was on their side.

* * *

Muzan looked around and could only frown in irritation; in front of him were five new figures. A shirtless boy with a boar mask, a black-haired girl with pink eyes and a purple kimono, a white-haired man with an eyepatch and jewels, an older man with a red mask and a blue patterned jacket, and a man with unruly orange-red hair and eyes donning a flame-guard on his drawn katana. It was apparent that the first two were responsible for killing Douma, the white-haired man did face Gyutaro and Daki a while back, and one of them looked almost exactly like an older version of the pillar that Akaza killed before his own undoing.

It did not matter, just like the last fool he faced, they would all be going down regardless of their numbers, "I'm guessing that the Cavalry has arrived. However, unfortunately for you, a bandwagon of insects will be nothing of a thread…" Before he could finish his mockery of the newly arrived heroes, he only saw a spark of lightning before he felt his arm fall to the ground in a bloody heap. With his mouth agape in subtle surprise, he turned around to see a yellow-haired boy with a matching colour jacket in a stance with his back facing the Demon Lord's own.

"Before you end the opening ceremony, make sure that everyone has made their appearance first. _Breath of Thunder: First Form: Thunderclap Flash._" The seriousness yet coolness in his tone was a bit shocking for his appearance, but Muzan could only frown at the disrespect that he was receiving for this day. Spinning on his heel, Muzan began to take in everything—all what happened for the day, and how he, the superior overlord of the world, was being constantly disrespected. His legion was destroyed, he was forced to go into his full power, and still, these insignificant insects could find ways to annoy him without them all dying under his heel.

Then he spotted him, and for the first time in what seemed like years, the white-haired monster gasped as his eyes took in what seemed like the apocalypse itself. The red hair, the drawn sword, and the Hanafuda earrings. Impossible… how could this be? He thought they were dead. How was Tanjirō still alive? Not only that, he saw the bright silhouette of that man that defeated him many centuries ago… no, it could not be.

Growling, he took in another sight; that girl that he went after almost three years ago. The same demon who had the answer to his only weakness, she was now standing nearest his most hated enemy. Then slowly, everyone began to gather behind them in organized fashion. All of those insects that could fight were there. However, Yoriichi's silhouette was not the only one he saw… he saw many more. The two boys that Kokushibo recently killed off, the one Akaza killed a while back, the girl Douma ate a few hours ago, Obanai Iguro, and a peach-haired boy with a fox mask. They all gathered in fighting poses, every last one of them—alive or dead—with their swords drawn and the glare of pure but controlled malice to the demon lord.

"Muzan Kibutsuji… you have ruined the lives of many in your long and terrible reign without much disturbance in your way. However, today marks a new day where this all ends. A new era where the lives of all those who were tormented shall be avenged, _and the mark of the day where you'll be sent to hell to face eternal judgement for your undisputed sins!_" The red-haired boy spoke, blood staining his clothes and face, but with rejuvenation gracing his eyes. With that being said, his sword burned a flame that torched the darkened sky.

Glaring, Muzan could only chuckle as he stared back, showing that he was not intimidated in the slightest. "Oh, how you all speak big… well show me that your actions can match your words for once…" A gasp left along his confidence as Tanjirou's flame tripled in size and illumination as the dark-haired girl placed her hand on top of the youth's clenched hand. His blade became a ferocious red as they both pointed the sword to Muzan, the flames crackling.

"Oh, we will… we will make sure that you'll regret every action when we do! **Now burn in hell, you bastard!**" With that being said, everybody opposing Muzan began to charge the sole villain as he readied himself into a fighting stance, a single bead of sweat dripping down his forehead for the first time as he knew that this battle may actually be his last if he weren't careful.

With that, a legendary battle would take place, but who would be the deciding victor; would good triumph or would evil continue to prevail?


End file.
